This invention relates to multipurpose photographic film handling cassettes in which an exposed film strip contained in the cassette may be processed, viewed by projection and rewound automatically without removal from the cassette in accordance with information supplied by the condition of the cassette and the film strip contained therein. More particularly, it concerns an improved arrangement for the initially sealed processing fluid containing reservoir arrangement which forms part of the film processing organization of such cassettes.
Multipurpose photographic film cassettes have been developed for use in cinematographic systems illustrated and described, for example, in U.S. Pat. No. 3,615,127 issued to Edwin H. Land on Oct. 26, 1971; U.S. Pat. No. 3,623,417 issued Nov. 30, 1971, to Vaito K. Eloranta; U.S. Pat. No. 3,785,725 issued Jan. 15, 1974 to John F. Batter, et al.; U.S. Pat. No. 3,895,862 issued July 22, 1975 to Joseph A. Stella, et al.; and U.S. Pat. No. 4,105,307 issued to William A. Holmes, et al. on Aug. 8, 1978, all of which are owned by the assignee of the present invention.
In such systems, a strip of photographic film contained a cassette can be exposed in a camera adapted to receive the cassette and then processed to provide viewable images by placing the cassette in a viewing apparatus equipped to activate a cassette-contained processor upon rewinding the exposed film strip. After processing in this manner, the viewing apparatus is operated as a projector to advance the film incrementally frame by frame past a light source so that the scene to which the film was exposed is reproduced in a manner well known in the motion picture art.
In systems of the type aforementioned, the processing operation after film exposure and before viewing entails the deposition of a uniform coating of processing fluid along the length of the film strip to effect a diffusion transfer of a negative image in a light sensitive emulsion layer on the film strip to a positive image receiving layer or interface. The processing fluid supply is contained in an initially closed reservoir or pod housed within the film cassette. The reservoir is provided with a removable tear tab closure capable of being opened upon activation of the processor by the viewing apparatus to allow the fluid to escape from the pod and pass through a nozzle-like opening against the exposed emulsion layer on the film strip. Although the processor is operated only once in only single cassette, the housing of which provides a permanent container for the film strip therein, its operation to achieve a uniform and complete layer of processing fluid over the exposed emulsion layer on the film strip is vital to satisfactory operation of the overall system since any defect in the operation of the processor will result in undesirable and permanent blemishes plainly observable during projection of the processed film.
In such systems, the processing fluid reservoir has been provided with a substantially vertically extending opening covered by a releasably bonded tear tab closure capable of being completely peeled from the opening to release the processing fluid for distribution against the emulsion layer of the exposed film strip. In prior systems of the type mentioned above, the tear tab initially sealing the processing fluid reservoir extends from one end of the reservoir opening to the other at which it is folded back upon itself to facilitate the removal thereof by pulling the folded-back portion.
As described in the above-noted U.S. Pat. No. 3,895,862, no viewer-mounted or other external means is needed for effecting the release of processing fluid from the initially sealed storage reservoir to initiate the processing cycle automatically upon rewinding the film strip after exposure in the cassette. The release of processing fluid from the reservoir is brought about by a pull strip extension connected at one end to the folded-back portion of the reservoir sealing tear tab and having at its free end, a configuration adapted to engage an aperture formed in the trailing end portion of the film strip attached to the supply spool during initial rewind rotation of the supply spool. The pull strip, which may be mylar or other similar material having the physical characteristics of a photographic film strip, is initially supported and constrained to an essentially S-shaped tortuous path in which the intermediate leg is established by a channel formed by internal cassette walls. The pull strip accordingly extends initially upward in confronting relation with the tear tab, then makes a downward turn passing through the aforementioned channel and makes a second turn at the lower end thereof before exiting from the channel. At its exit from the channel, the extension is bent back on itself without exceeding the elastic limits of the material from which it is made so that the projecting free end lies yieldably against the outer convolutions of the film strip on the supply spool. As the film strip pays out from the supply spool during exposure, the free end of the pull strip will move inwardly due to the diminishing diameter of film strip convolutions on the supply spool until the film strip is completely exposed. At this time, an aperture in the supply spool connected trailing end portion of the film strip will have passed the free end of the pull strip extension so that upon rewinding of the film strip back onto the supply spool, a latching tongue at the free end of the pull strip will engage in the film strip aperture and become entrained between successive convolutions of the film strip supply spool trailing end portion. Continued rewind rotation of the supply spool will effect a pulling action on the pull strip causing it to advance through the S-shaped tortuous path and correspondingly, resulting in peeling of the tear tab closure from the processing fluid resevoir to release the processing fluid for application thereof to the exposed film strip. After having been peeled completely from the processing fluid reservoir, the tear tab is disengaged from the pull strip by a knife-like formation at the exit of the channel formed by the internal cassette walls. The removed tear tab closure will remain in a storage chamber defined by the channel once the processing cycle has been complete.
In order to define the above-noted S-shaped path at the processing station, a plurality of internal cassette transverse wall formations which form an integral part of the cassette have been necessitated. Further wall formations have been utilized in order to define a pair of chambers, one communicating to the processing fluid applicator nozzle and a second defining an initially sealed reservoir for the processing fluid which opens along one upright side of this chamber at a planar face to which the releasable tear tab closure is initially fixed. In practice, the fluid chamber actually provides an internal receptacle for a prefabricated and self-contained pod of processing liquid to which the tear tab closure is affixed. In this way, cassette assembly is facilitated by placing the pod in the chamber, threading the tear tab through the S-shaped path and then sealingly attaching a reservoir top to the upstanding wall formations defining the S-shaped path and the pair of fluid chambers.
It should be appreciated, accordingly, that in order to achieve reliable operation of such a processor, careful attention to assembly of the processor is necessary; the concommitant cost associated with such assembly is not insignificant.
In order to assure reliable separation of the tear tab from the processing fluid reservoir, a number of arrangements have been implemented in order to minimize drag as the pull strip passes through its path. One such example is illustrated in U.S. Pat. No. 4,110,018 to F. M. Finnemore and assigned to the assignee of the present invention wherein low friction guide arrangements are provided to guide the pull strip along its desired path. Such an arrangement, of course, requires added piece parts, additional assembly steps and accordingly, further added cost to the final assembled cassette.